You make a declaration on your annual state income tax return.
There is no treaty -- There is only an OECD dictate and an EU interpretation. The EU law in unenforceable in any US Court jurisdiction. The EU is relying on foreign businesses voluntary taxation compliance -- voluntary taxation compliance which you have previously said is silly
All sales and VAT taxes are regressive. The lower your income is the greater percentage of your income is used to pay these consumption taxes.
This is for the USA:
VAT tax is similar -- it costs lower income people the most. VAT tax like sales tax -- the same rate for everyone rich or poor.
This will end up hurting international trade.
I don't want reciprocal taxation for 100 countries (and 50 USA states) that we do business with. We would need to add 15 accountants and bookkeepers -- what does that cost and why should our business support every tax law in the world? We comply with the tax laws of the jurisdictions we are domicile in. Every business does.